Chapter 2 Estimation and Number Theory

Find each sum or difference. Then use rounding to check that your answers are reasonable. Round each number to its greatest place value.

74 + 53 =

• Estimated value:

  120

• Estimated value:

  130

• Estimated value:

  110

• Estimated value:

  127

Find each sum or difference. Then use rounding to check that your answers are reasonable. Round each number to its greatest place value.

216 - 39 =

• Estimated value:

  170

• Estimated value:

  160

• Estimated value:

  160

• Estimated value:

  180

Find each sum or difference. Then use front-end estimation to check that your answers are reasonable.

23 + 64 =

• Estimated value:

  90

• Estimated value:

  80

• Estimated value:

  70

• Estimated value:

  85

 

Find each sum or difference. Then use front-end estimation to check that your answers are reasonable.

926 - 654 =

• Estimated value:

  200

• Estimated value:

  250

• Estimated value:

  270

• Estimated value:

  300

 

Find each sum or difference. Then use front-end estimation to check that your answers are reasonable.

8,142 + 3,154 =

• Estimated value

  11,000

• Estimated value

  12,000

• Estimated value

  11,500

• Estimated value

  10,000

Find the product or quotient. Then estimate to check that your answers are reasonable.

42 x 3 =

• Estimated value:

  130

• Estimated value:

  120

• Estimated value:

  110

• Estimated value:

  140

• Estimated value:

  20

• Estimated value:

  30

• Estimated value:

  40

• Estimated value:

  25

The Greatest Common Factor of 16 and 36 is:

• 12

• 2

• 3

• 4

7 X 8 =

• 56

• 49

• 48

• 42

What is the fourth multiple of 7?

• 35

• 84

• 28

• 24